A method for generating control pulses for power semi-conductors, in particular for the purpose of generating offset control pulses for half-bridges which are coupled to multiphase converters or to DC to DC voltage converters, is described in German Patent Application No. DE 101 10 615 A1. In this method, the reference voltage is displaced by a delay time corresponding to the staggerings or a PWM signal is displaced by a delay time which corresponds to the period divided by the number of offsets.
A device for supplying power to a multi-voltage on-board electrical system of a motor vehicle is described in German Patent Application No. DE 101 19 985 A1. This device has a multi-voltage on-board electrical system situated in a motor vehicle which provides at least one first and one second voltage level, each being different from the reference potential. The multi-voltage on-board electrical system is supplied from at least one electrical energy accumulator. Moreover, it has at least one converter for connecting the two voltage levels. Furthermore, a supply arrangement for external power supply into the multi-voltage on-board electrical system is provided. The above-mentioned converter may be implemented in the form of a multiphase converter. In converters of this type, multiple converter cells of lower power are connected in parallel and the power sections are clocked with a time offset. Due to extinction effects, filter modules may be saved here. Multiphase converters of this type make it possible to implement the first converters and the second converters with the existing phases of a single multiphase converter. For this purpose, the phases are divided here into converters with up and down converting functions. The phases are then separated inside the converter via a switch at the input.
High-performance DC to DC voltage converters are needed in future on-board electrical systems in motor vehicles in order to be able to regulate the power flow between different voltage levels. Due to cost, installation space, and weight limitations, such use in the automotive industry requires minimization of the inductivities and capacitances as well as of the number of components overall. These limitations may be met by using multiphase DC to DC voltage converters as DC to DC voltage converters in which the power to be transmitted is distributed to multiple converter cells. If time-offset clocking of the converter cells is used with this principle, then the current ripples in the superimposed output signal partially cancel out each other or are reduced by a substantial value. The frequency of the output signal of the DC to DC voltage converter increases by the number of the converter cells clocked with a time offset compared to the base clock frequency of the converter cells. The output filters of the DC to DC voltage converter may have smaller dimensions due to the smaller ripples and the higher frequency, whereby cost and installation space advantages are achieved.
For efficient utilization of this method, one current sensor must be used for each converter cell to be able to monitor and regulate the respective current ripples. Without such a single phase regulation, the ripples for each phase may have different magnitudes whereby the above-discussed advantage in the superimposition of the output signals is no longer effective. The ripples in the output signal are getting greater and the frequency of the output signal reverts to the same value as the switching frequency of the individual converter cells, whereby the previously mentioned advantages are canceled out again.